Decrease in neutralizing antibody titers after SARS-CoV-2 vaccination in hemodialysis patients and the booster effect of a third vaccination

We measured anti-SP-IgG antibody titers 6 months after the second dose of a SARS-CoV-2 vaccine (BNT162b2) and 1 month after the third vaccination in 105 hemodialysis patients, and examined the booster effect of the third vaccination. The mean anti-SP-IgG antibody titer at 6 months after the second vaccination was 499.2±619.4 AU/mL, which was about one-tenth lower than that seen 1 month after the second vaccination；however, 7 patients exhibited negative conversion (＜50 AU/mL). The mean anti-SP-IgG antibody titer at 1 month after the third vaccination, including the cases involving negative conversion, had increased 85.7 times to 42,800.9±58,666.2 AU/mL, confirming the booster effect of the third vaccination. However, although the causes were unknown, there were two unresponsive cases.